The present invention relates to an instrument measuring the orientation of those inclusive of sheet-like substances such as a polymer sheet including a film and paper and stereoscopic articles such as moldings of plastic, resin, rubber and the like with a microwave.
The fiber orientation of paper corresponds to the chain direction of molecules forming fiber, and is closely related with curling, torsion, inclination of NIP (Non-Impact Printer) paper and the like. Standards in fiber orientation are becoming strict particularly in these several years, and several types of measuring methods have been employed. There are a water diffusion method, a dynamic rupture intensity method, an ultrasonic method, a microwave method and the like as such measuring methods, and the correspondence between operations on a wire part and the orientation is substantially being elucidated at present.
On the other hand, in the case of a polymer film, that forming the film is not fiber, and anisotropy of the arrangement of molecular chains can be grasped as the anisotropy of various physical properties, for example, optical, electrical and mechanical intensity and the like. Therefore, inclusive of paper, polymer film and the like, the orientation can be collectively grasped as the anisotropy (molecular orientation) of the arrangement of molecular chains.
It is general that a solid polymer has orientation in the process where molecular chains are solidified from a fluidized state due to the shape thereof. Due to the orientation, anisotropy appears in a dynamic, thermal, optical or electromagnetic physical property. Consequently, for example, anisotropy of the modulus of elasticity, anisotropy of the ratio of heat contraction or the like, takes place to cause various problems in quality.
As methods of measuring such anisotropy, an X-ray diffraction method, an infrared polarization method, a fluorescence polarization method, a birefringence method, an ultrasonic method, a microwave method and the like are employed.
Among these methods, the X-ray diffraction method and the fluorescence polarization method require time and labor for measurement, while measurement is difficult in relation to a thick sample in the infrared polarization method. The birefringence method is a method of optically measuring anisotropy by utilizing a refraction phenomenon based on anisotropy of a refraction index, and an opaque sample cannot be measured since transparency with respect to visible light or near infrared light is required for measurement. The ultrasonic method is of a contact type and hence unsuitable for a moving sample.
A method employing resonance of a microwave utilizes anisotropy of a dielectric constant The dielectric constant has a constant relation also with a refractive index. The method employing a microwave is utilized for molecular orientation measurement regardless of presence/absence of optical transparency inclusive of paper and a polymer film.
FIG. 1 illustrates the principle of a conventional orientation meter employing a microwave cavity resonator. It comprises a microwave introduction part 2 on one end portion and a microwave detection part 4 on another end portion. The part between these end portions defines a microwave resonator 6 formed by a waveguide having a constant electric field vibrational direction. The resonator 6 is provided with a slit 8 in a direction perpendicularly crossing the axis of the resonator 6 on the position of a loop part of a standing wave. A sample 10 is arranged in the slit 8, a microwave is introduced from the microwave introduction part 2, and the microwave intensity is detected with the microwave detection part 4. The sample 10 is rotated around the axis of the resonator 6, and the intensity of the transmitted microwave is detected every rotational angle for obtaining the orientation pattern. It is also possible to obtain a dielectric constant pattern by obtaining the dielectric constant every rotational angle position from deviation between the resonance frequency when arranging the sample 10 in the slit 10 and the resonance frequency when arranging no sample.
As a method of measuring the dielectric constant with a microwave, that shown in FIG. 2 is proposed (refer to Japanese Utility Model Laying-Open Gazette Jitsu Kai Hei 3-70368). There, it comprises a pair of dielectric resonators 12a and 12b opposite to each other through a sample 10. A pair of terminals 14a and 14b oppositely arranged through the dielectric resonator 12a are provided on side portions of one dielectric resonator 12a. An electric field vector having one direction parallel to the plane of the sample 10 is generated in the dielectric resonators 12a and 12b by these terminals 14a and 14b, for measuring the dielectric constant from the resonance characteristics thereof. Here, the terminals 14a and 14b are loop-like. It is also possible to comprise a plurality of pairs of terminals 14a and 14b and measure dielectric anisotropy of the sample by switching operations thereof.
In the measuring instrument shown in FIG. 1 or FIG. 2, cavity resonators or dielectric resonators are oppositely arranged on both sides through the sample 10, and hence the shape of the measured sample 10 is limited to a sheet-like one.
Accordingly, a first object of the present invention is to make it possible to measure dielectric anisotropy not only in a sheet-like sample but also in a sample such as a stereoscopic molding.
An electric field vector in an in-sample plane required is desirably more uniform during measuring the dielectric anisotropy.
While the terminals 14a and 14b are loop-like in the measuring instrument shown in FIG. 2, a second object of the present invention is to find a terminal shape which can further attain uniformity of an electric field vector than the loop-like terminal and improve sensitivity of dielectric anisotropy measurement.
One aspect of the present invention comprises a dielectric resonator having a plane being close to or being in contact with a sample, a microwave exciter generating an electric field vector having a unidirectional component at a frequency in the vicinity of the resonance frequency of the dielectric resonator when the sample is present and in an in-sample plane parallel to the said plane in the dielectric resonator, a detector detecting transmission energy or reflection energy by the dielectric resonator, a rotation mechanism rotating the sample or the dielectric resonator in a plane parallel to the said plane, and a data processor obtaining dielectric anisotropy of the sample from variance of a detection output of the detector following rotation by the rotation mechanism.
This aspect is suitable for obtaining the dielectric anisotropy of a specific part of the sample.
Another aspect of the present invention comprises a plurality of dielectric resonators comprising planes being close to or being in contact with a sample and arranged close to each other, a microwave exciter generating electric field vectors having unidirectional components, which are electric field vectors having directions different from each other at a frequency in the vicinity of the resonance frequency of the dielectric resonators when the sample is present and in an in-sample plane parallel to the said planes in the respective dielectric resonators, detectors for the respective dielectric resonators detecting transmission energy or reflection energy by these dielectric resonators, and a data processor obtaining dielectric anisotropy of the sample from variance of detection outputs by the detectors at the electric field vectors of different directions from the plurality of dielectric resonators.
According to this aspect, neither the sample nor the dielectric resonators may be rotated but the dielectric anisotropy of the sample can be obtained by outputs from the plurality of dielectric resonators, whereby it is suitable for continuously measuring a sample flowing online.
Still another aspect of the present invention comprises a dielectric resonator having a plane being close to or being in contact with a sample, a plurality of sets, which are sets of microwave exciters generating electric field vectors having unidirectional components at a frequency in the vicinity of the resonance frequency of the dielectric resonator when the sample is present and in an in-sample plane parallel to the said plane in the dielectric resonator and detectors detecting transmission energy or reflection energy by the dielectric resonator, arranged on positions different from each other with respect to the dielectric resonator, a switching driver selecting one set among the plurality of sets of microwave exciters and detectors and sequentially driving the same, and a data processor obtaining dielectric anisotropy of the sample from variance of detection outputs of the detectors following switching by the switching driver.
According to this aspect, neither the sample nor the dielectric resonator may be rotated but the dielectric anisotropy of the sample can be obtained by switching operations of the sets of the microwave exciters and the detectors by the switching driver, whereby it is suitable for continuously measuring a sample flowing online also in this case.
Variance of the detection output by the detector can be measured as variance of the resonance frequency. The variance of the resonance frequency can be measured as the shift quantity of the frequency itself. The variance of the detection output by the detector can also be detected as variance of detection energy at a specific frequency.
Terminals of the microwave exciter and the detector can be rendered loop-like, or can be rendered rod-like terminals. When loop-like, coupling occurs through magnetic field, and when rod-like, coupling occurs through electric field. Electric field distribution on the position of the sample is decided by a resonance mode determined by the shape, the magnitude, an excitation method, the dielectric constant etc. of the dielectric resonator, and hence it is desirable to select such a resonance mode that an electric field as parallel as possible to the plane being close to or being in contact with the sample is produced.
The loop-like or rod-like terminals may be so arranged that the directions of magnetic field distribution or electric field distribution in the resonance mode to be resonated and the magnetic field or the electric field produced by the loop-like or rod-like terminals vectorially coincide with each other, and are preferably arranged in the vicinity of or inside the dielectric resonator. For example, rod-like terminals can be arranged in a direction perpendicular or parallel to the plane of the dielectric resonator being close to or being in contact with the sample.
When detecting transmission energy with the detector, the exciter and the detector are connected respectively to a pair of loop-like or rod-like terminals oppositely arranged through the dielectric resonator.
Furthermore, when detecting reflection energy with the detector, the exciter and the detector are connected to one common loop-like or rod-like terminal arranged close to the dielectric resonator.
The dielectric resonator is a cylindrical resonator or a square resonator.
The periphery of the dielectric resonator is preferably covered with a shielding material consisting of a conductive material except a sample measuring surface. Thus, the Q value of a resonance curve can be increased. At this time, it is preferable that a shielding material consisting of a conductive material is arranged also above a sample measuring surface of the dielectric resonator so that the sample is arranged between the sample measuring surface of the dielectric resonator and the shielding material above the sample measuring surface.
FIG. 3(A) schematically shows one embodiment With respect to a dielectric resonator 20, proper microwave loop antennas (or rod antennas) 22a and 22b are arranged on proper positions in proper directions with respect to the dielectric resonator 20. It is possible to produce a resonance mode resonating the dielectric resonator 20, where an electric field vector leaking outward from the resonator 20 is present, by the antennas 22a and 22b. For resonance modes, there is a TM mode or a TE mode when the dielectric resonator 20 is square, and there is an HEM mode or the like when it is cylindrical. The intensity of an electric field vector 24 substantially exponentially decreases as separating from the dielectric resonator 20, while the resonance frequency shifts by electromagnetic coupling in response to the dielectric constant of a sample by placing the sample 25 in separation from the dielectric resonator 20 by a small distance or in contact with the dielectric resonator 20.
FIG. 3(A) schematically shows the structure in the case of employing a cylindrical dielectric resonator as the dielectric resonator 20 and making an HEM11xcex4 mode, while a microwave going out from an oscillator 26 generates an electric field through the loop antenna 22a, and the dielectric resonator 20 resonates by electromagnetic coupling. The resonance frequency in this case is decided by the dimensions and the dielectric constant of the dielectric resonator 20. Assuming that the radius of the cylinder of the dielectric resonator 20 is a, the length is L and the dielectric constant is ∈, the resonance frequency f (GHz) is approximately obtained as:
f=34(a/L+3.45)/a/∈xc2xd
FIG. 3(B) expresses FIG. 3(A) as an equivalent circuit. With respect to the resonance frequency when placing no sample, the resonance frequency shifts by the capacitance Cr changing in response to the dielectric constant of the sample 25 when placing the sample 25. When the dielectric constant of the sample 25 has anisotropy, the resonance frequency also shifts with depending on the directions of the sample 25 and the electric field vector 24.
FIG. 4 shows electric field distribution in the HEM11xcex4 mode. (A) shows electric field distribution on a horizontal plane around an end of the dielectric resonator 20, and (B) shows electric field distribution on a meridian section plane of xcfx86=0 (xcfx86: angle from a reference direction in the horizontal plane).
Returning to FIG. 3 and making description, the microwave going out from the oscillator 26 is magnetically coupled with the dielectric resonator 20 by the loop antenna 22a, and the dielectric resonator 20 can enter a resonant state. The electric field vector of the dielectric resonator 20 appears in the form substantially parallel to the plane of the sample 25, and interaction with a dipole moment provided in the sample 25 takes place. Here, with rotating the sample 25 or the dielectric resonator 20 in parallel planes of the sample 25 and the dielectric resonator 20 by detecting microwave intensity appearing in a detector 28 in correspondence to its rotational angle, the orientation state can be obtained from angle dependency of the intensity. A controller 30 controls the frequency of the microwave generated from the oscillator 26 and captures the microwave intensity by the detector 28. 32 is a computer as a data processor obtaining the orientation state from the angle dependency of the detected microwave intensity.
The principle of orientation measurement is further described. In the dielectric resonator 20, there is relation shown in FIG. 5(A) between the intensity of the transmitted microwave and the frequency. This resonance curve is referred to as a Q curve. With the sample 25 being placed, the Q curve varies by the following relation:                     ω        -                  ω          a                            ω        a              ≅                  1                  4          ⁢                      W            _                              ⁢                        ∫                      Δ            ⁢                          xe2x80x83                        ⁢            V                          ⁢                              [                                                            (                                      P                    +                                          J                                              jω                        a                                                                              )                                ·                                  E                  a                  *                                            +                                                μ                  0                                ⁢                                  M                  ·                                      H                    a                    *                                                                        ]                    ⁢                      ⅆ            v                                          W      _        =                  1        2            ⁢                        ∫          V                ⁢                              ϵ            0                    ⁢                                    "LeftBracketingBar"                              E                a                            "RightBracketingBar"                        2                    ⁢                      ⅆ            v                                    ω    =          2      ⁢      π      ⁢              xe2x80x83            ⁢      f            ω    ⁢          :          ⁢    complex    ⁢          xe2x80x83        ⁢    angular    ⁢          xe2x80x83        ⁢    frequency    ⁢          xe2x80x83        ⁢          (      sample      )                  ω      a        ⁢          :          ⁢    complex    ⁢          xe2x80x83        ⁢    angular    ⁢          xe2x80x83        ⁢    frequency    ⁢          xe2x80x83        ⁢          (      blank      )            P    ⁢          :          ⁢    electric    ⁢          xe2x80x83        ⁢    polarization        J    ⁢          :          ⁢    conductive    ⁢          xe2x80x83        ⁢    current    ⁢          xe2x80x83        ⁢    density              E      a        ⁢          :        ⁢          xe2x80x83        ⁢    electric    ⁢          xe2x80x83        ⁢    field        M    ⁢          :          ⁢    magnetic    ⁢          xe2x80x83        ⁢    field              H      a        ⁢          :          ⁢    magnetization    ⁢          
        *          :          ⁢    indicates    ⁢          xe2x80x83        ⁢    that    ⁢          xe2x80x83        ⁢    it    ⁢          xe2x80x83        ⁢    is    ⁢          xe2x80x83        ⁢    a    ⁢          xe2x80x83        ⁢    complex    ⁢          xe2x80x83        ⁢    number  
That showing the variance is FIG. 5(B). When the sample 25 has anisotropy in a plane opposite to the dielectric resonator 20 and if the sample 25 or the dielectric resonator 20 is rotated in a plane parallel to the plane, the peak frequency (resonance frequency) of the Q curve varies every relative rotational angle position (S) of the sample 25 with respect to the dielectric resonator 20 as shown in FIG. 6(A), for example. In this rotation, in a Q curve shifting to the highest frequency side, for example, it is assumed that detected intensity of the transmitted microwave at the frequency is l and such a frequency that detected intensity on the high frequency side is l/2 is f1. The detected intensity of the transmitted microwave at each rotational angle at the frequency f1 is shown as a section of FIG. 6(B). Rewriting it with the rotational angle S on the horizontal axis, it becomes as shown in FIG. 7(A). Further rewriting it in a spherical coordinate system, it becomes elliptic as shown in FIG. 7(B), and the orientation angle (xcfx86) and the degree of orientation (a/b) can be obtained from this result. a is the major axis length of the elliptic, and b is the minor axis length.
The present invention comprises a dielectric resonator having a plane being close to or being in contact with a sample, and rotates the sample or the dielectric resonator in the plane or changes the direction of an electric field vector while generating the electric field vector having a unidirectional component at a frequency in the vicinity of the resonance frequency of the dielectric resonator when the sample is present and in an in-sample plane parallel to the plane. Alternatively, it comprises a plurality of dielectric resonators having planes being close to or being in contact with a sample and arranged close to each other, and generates electric field vectors having unidirectional components which are electric field vectors having directions different from each other at a frequency in the vicinity of the resonance frequency of the dielectric resonators when the sample is present and in in-sample planes parallel to the planes in the respective dielectric resonators. Then, it obtains dielectric anisotropy of the sample from variance of a detection value of resonance energy following rotation of the sample or the dielectric resonators or change of the electric field vectors or detection values of resonance energy from the plurality of dielectric resonators having different directions of electric field vectors. Thus, it is possible to measure dielectric anisotropy not only in the case where the shape of the sample is a sheet-like one but also in a sample such as a stereoscopic molding.
A moving sample can be continuously measured by rotating the dielectric resonator, changing the direction of the electric field vector or arranging a plurality of dielectric resonators having different directions of electric field vectors, so that it is applicable to online measurement on the production site.
Also, when the dielectric resonator is covered with a conductive shielding member except a part where the sample is arranged, Q of a resonance spectrum increases and measurement with a considerate S/N ratio is enabled.